1. Field of the Invention
The present invention relates to thermal printing techniques, and more particularly, to thermal print heads of the thermal sublimation/transfer printers and associated control methods.
2. Description of the Prior Art
In general, color printers can be classified into four major categories: dot matrix printers, inkjet printers, laser printers, and thermal sublimation (or thermal transfer) printers. Recently, the thermal sublimation printers have become increasingly popular due to their full tone printing performance. A thermal sublimation printer drives its thermal print head (TPH) to heat ribbons containing dyes to transfer the dyes onto an object to be printed. By this way, continuous-tone can be formed on the object according to the heating time or the heating temperature.
Please refer to FIG. 1, which shows a schematic diagram of a conventional thermal print head 100. As shown, the thermal print head 100 is provided with a plurality of driver circuits 110. Each driver circuit 110 loads printing data in accordance with an operating clock signal and then latches the loaded data under the control of a latch signal. Afterward, a strobe signal is employed by the thermal print head 100 to control each driver circuit 110 to drive coupled plural heating elements. Each heating element is arranged for heating an image dot, i.e., a pixel of the image to be printed. While the thermal print head 100 prints pixel data of a row, all driver circuits are controlled by the strobe signal to simultaneously drive corresponding heating elements. Therefore, considerable power consumption is required for supporting such operation of the thermal print head 100.
One conventional method for reducing the power consumption of the thermal print head 100 is to divide the image data of a row into two parts: one part is composed of odd pixels while the other part is composed of even pixels. Then, the two parts are printed in turn. For example, the thermal print head 100 can firstly print odd pixels of a row and then print even pixels of the row after the odd pixels are printed completely. Such a printing method can reduce the required power consumption of the thermal print head 100, but it doubles the printing time and increases the complexity of the firmware control of the thermal sublimation printer.